THE EOCENE PERIOD. 243 



cated, was made up largely of the coin-like Nummalites, which lived in 

 prodigious abundance. The gastropods and pelecypods of modern types 

 became very prolific, while the cephalopocls were markedly less impor- 

 tant than in the Cretaceous. The nautiloids were more abundant than 

 now, while the sepioids have left little record. The sea-urchins con- 

 tinued to be abundant, the corals had taken on the modern forms, and 

 the decapods were rising in importance. 



The American Eocene faunas were rather pronouncedly provincial, 

 though there was a minor list of species of rather wide range, binding 

 the provinces together. This condition is assignable to the previous 

 restrictive movement, and to the fact that the shallow-water tract was 

 only a border belt and subject to much variation from point to point. 

 So true is this, that much difficulty is experienced in making a confident 

 correlation between the formations in different sections even along 

 the Atlantic and Gulf coasts. Much greater difficulties arise when 

 the regions are more widely separated. The variations are, however, 

 variations of detail, not of broad features that can be readily sketched. 

 For these, reference must be had to the paleontological reports on the 

 regions involved. 1 



The Oligocexe Epoch. 



In North America. — As already stated, formations corresponding to 

 the Oligocene of Europe have not usually been differentiated, in North 

 America, from the Eocene below and the Miocene above. Recently, 

 however, the differentiation has been gaining ground, and may be jus- 

 tified for the reasons set forth on pages 194-5, or on paleontological 

 grounds, if it is desirable to make the classification for this country 

 conform as closely as possible with that of Europe. 2 



Certain beds along the Atlantic coast (Cooper River marl, and per- 



1 W. H. Dall, Tertiary Fauna of Florida, Trans. Wagner Free Inst. Sci., Vol. Ill, 

 Pts. 1-5, 1890-1900, finely illustrated; Bull. 141, U. S. Geol. Surv., 1896, and other 

 papers therein referred to. W. B. Clark, Md. Geol. Surw, Eocene volume, 1901, 

 finely illustrated, full bibliography, q.v. R. M. Bagg, Bull. 141, U. S. Geol. Surv., 

 1896, Protozoa. A. Heilprin, Comp. Eocene Mollusca of Ulwich, Europe, Proc. Acad, 

 Nat. Sci. Phil., Vol. XXXI, 1879; Vol. XXXII, 1880; and Vol. XXXIII, 1881; Jour. 

 Acad. Nat. Sci. Phil., Vol. IX, 1884. T. W. Vaughn, Ccelenterata, Bull. 141, U. S. 

 Geol. Surv., 1896; Corals, Mon. XXXIX, U. S. Geol. Surv., 1900. T. W. Stanton. 

 Eocene of Pacific Coast, 17th Ann. Rept. U. S. Geol. Surv., Pt, I, 1895-6. Gilbert 

 D. Harris, Am. Pal. Bull., Vols. I and II. 



2 For table of Oligocene formations, see Dall, 18th Ann. Rept. U. S. Geol. Surv., 

 Pt. II. 



